Synthetic turf has been used for many years as surfaces for football, baseball, and soccer fields. In the recent years it has been used in other applications where an alternative to natural grass is desired. These applications include at least playgrounds, residential and commercial lawns and other landscaping, paths, paintball fields, tennis courts, putting greens, dog runs etc.
Typically, synthetic turf includes a grass-like fabric having a backing and a plurality of upstanding ribbons, also called face fibers, resembling grass. Many synthetic turf products also include an infill material dispersed among the upstanding ribbons, which may consist of sand, tire rubber crumb, or other particulates, either singularly or in combination with each other. The infill material simulates the soil in natural turf, acts as a ballast, and/or contributes to the physical properties of the turf, such as resiliency, that make the turf suitable for a particular use.
Synthetic turf has a limited life span, depending on the construction of the turf, the application for which it is used, weathering and how the turf is maintained.
As an example, a typical synthetic turf for use as an athletic field may have a useful life of from about 8 to 15 years. A large amount of synthetic turf is currently being used in hundreds of athletic fields and in other applications.
Disposing of the turf is very expensive due to the composition of materials ranging from recycled rubber over sand to plastic. To avoid sending that turf to landfills at a substantial cost, recycling and reusing all or portions of the synthetic turf has been an explored option over recent years.
Methods for recycling carpets and for preparing carpet backing using recycled carpet scrap are known. Some of such methods involve separating the carpet yarns, or tufts, from the backing, e.g. by cutting, and processing only yarns.
However, synthetic turf differs in composition from carpet, and those differences in composition make conventional carpet recycling processes unsuitable for recycling synthetic turf. The majority of carpet products use nylon face fibers, while the majority of current synthetic turf products use polyethylene.
The primary coating of most carpets is a latex coating, while the coating in most synthetic turf is polyurethane. In the United States, only a small fraction of broadloom carpet includes a coating containing polyurethane, and only a small fraction of synthetic turfs have a coating containing latex.
Most of the synthetic turf manufactured in the past 6 years has had a polyurethane coating applied to the backing. There is a belief that polyurethane coated synthetic turf as a whole cannot be recycled. This is because the polyurethane coating, cannot be efficiently recycled. Polyurethane is thermoset (versus thermoplastic) and is therefore difficult and costly to recycle.
Notwithstanding, recovery of polyurethane from carpets is described in U.S. Pat. No. 5,185,380 where the backing is scraped off, comminuted, subjected to a cyclone classification step to remove hard foreign constituents, such as metals and PVC, and the non-hard constituents are consolidated under elevated pressure and temperature to provide sheets. This method then provides a new product from parts of the used carpet.
In turf, the coating is applied to the backing of a tufted material for the purpose of locking the face fibers into the primary backing. An additional coating of a hot melt adhesive or a polyurethane foam can also be applied. This secondary coating is typically used to attach a secondary backing which can be polyester or polypropylene.
Many synthetic turf products include components that are not found in carpet and that are incompatible with, or at least undesirable in, conventional carpet recycling methods. For example, conventional carpet does not include infill. Typical infill materials for synthetic turf installations include sand, tire rubber crumb, and/or other particulates, either singularly or in combination with each other. Thus, recycling synthetic turf presents a unique problem not encountered in the recycling of carpet.
Separating infill from the remainder of the turf may require use of special equipment, and there may be environmental concerns associated with disposing of the separated infill. Additional concerns in the recycling process are the effect of any residual infill particulates on the size reduction process and on the properties of the final product.
Thus, attempts have been made to recycle and reusing an existing synthetic turf, or at least a portion of an existing synthetic turf, to avoid sending the entire synthetic turf to a landfill when it is no longer useful. Such a process is described in WO 2010/075098 in which infill is separated from the backing and the grass like fibers followed by downsizing and further removal of infill followed by agglomeration. The granules of agglomerated turf fragments are placed into an extruder. The granules are extruded to form an extrudate, for example in the shape of a strand or ribbon.
Most known processes consequently recycle the constituents of carpets or turfs to new products of mixed components and do not reverse engineer the products into the individual starting components.
Hence, existing processes can separate the materials to a purity of 95% only which is satisfactory when for example the process is for extruding/consolidating for providing new products. Thus, while the prior art processes are an improvement over disposing the material at the land fill, there is still a need to separate the individual parts further such as to fractions substantially comprising one component in order to provide improved grade products.
It is also desirable to provide processes that are flexible so that the composition of the turf and the infill may vary.
It is also desirable to provide processes in which the result is the individual components purified to a degree that is high enough for reuse as turf or in other industries.
Therefore, the aim of the present invention is to provide an improved process for separating constituents of various turf products and also to provide a process where the purity of each of the separated constituents exceeds 95% weight percent (wt %) to being essentially pure.